1. Technical Field
The present invention relates generally to an improved data processing system and in particular to a method and apparatus for handling storage media in a data processing system. Still more particularly, the present invention provides a method and apparatus for handling magnetic media in the form of a tape in a storage system.
2. Description of Related Art
One issue faced by the data processing industry is how to store the maximum amount of data on a minimum volume of media. Magnetic recording tape is commonly used as the media of choice because it is inexpensive and yet it provides significant data storage capacity per unit volume. Improvements in magnetic recording technology have increased the track density as well as the bit recording density for magnetic tape. These improvements have been used to maximize the number of bits stored per square inch of magnetic tape. Further improvements in the recording density of magnetic tape are increasingly difficult to attain because of the need for accurate alignments of the magnetic tape with the read/write head to read the data from the tracks written on the magnetic tape. Any misalignments of the tracks of the magnetic tape with the read/write head causes errors in the data read from the magnetic tape. In addition, the increase in linear recording density is restricted by the bandwidth of the recording channel.
One approach to increasing the amounts of data that may be stored on magnetic tape is to use a two-sided magnetic tape. On a two-sided magnetic tape, data is written on both sides of the tape. These types of systems, however, require two sets of read/write heads, with one set of read/write heads being located on each of the two sides of the magnetic tape as it travels through the tape path and the tape drive. These types of systems require specially designed tape drives. These tape drive systems are complex because they require the use of two sets of read/write heads to read and write both sides of the tape as it travels through the system. The increased number of components also increases the cost of creating such tape drive systems.
Therefore, it would be advantageous to have an improved method and apparatus for reading both sides of a media using a single set of read/write heads.
The present invention provides a method and apparatus in a data storage system for accessing a tape storage media wherein the tape storage media has a first side and a second side for storing data. The tape storage media is received at a reel. The reel is rotatable in a first direction and in a second direction, and the reel is positioned proximate to a head used to access the tape storage media as the tape storage media is wound onto the reel. The reel is selectively rotated in the first direction and the second direction to selectively present the first side and the second side for access by the head.
In the depicted examples, the reel includes an inner reel and an outer reel. The outer reel is rotatable in a first direction and in a second direction to selectively present one side of the tape to the head. The inner reel is rotatable to draw additional portions of the presented side of the tape on the outer reel past the head.